The present invention relates to a method of handling a photosensitive material in the form of a sheet, hereinafter referred to as "a photosensitive sheet" in which, after being photographically exposed, the photosensitive sheet is allowed to drop by its own weight in response to the opening of a cassette and the photosensitive sheet thus dropped is delivered into an automatic developing machine.
A variety of devices for automatically opening in a light room a cassette used for X-ray photography to remove a film therefrom and delivering the film to an automatic developing machine, hereinafter referred to as "automatic feeders", have been proposed in the art. However, such conventional automatic feeders are disadvantageous in that their work efficiency is still low.
Such feeders will be described in more detail. With the conventional automatic feeder, the film is handled as follows. The cassette is inserted into and taken out of the automatic feeder which has, in general, a light-shielded structure, by opening and closing its cover. The cover of the automatic feeder must be maintained closed until the film discharged by opening the cover of the cassette is delivered into the automatic developing machine. That is, the cassette cannot be removed from the automatic feeder until the film is perfectly delivered into the automatic developing machine. Thus, the conventional automatic feeder is disadvantageous in that the necessary waiting period which must elapse from the instant that the film is discharged from the cassette until the cassette is taken out of the automatic feeder is relatively long and the processing interval between the time the top edge of a film is discharged from the following cassette and the passing of the rear edge of a film discharged from the preceding cassette is excessively long. Therefore, the maximum processing ability of the automatic developing machine has not been fully utilized.
Accordingly, an object of the invention is to provide a method and apparatus for handling photosensitive sheets in which the above-described difficulties accompanying a conventional method have been eliminated, specifically, in which the period waiting from the instant that a photosensitive sheet is discharged from a cassette until the cassette is taken out of an automatic feeder is reduced to improve the work efficiency and the time interval for processing photosensitive sheets in an automatic developing machine is decreased to fully utilize the maximum processing ability of the automatic developing machine.
The invention relates also to a method and apparatus for delivering a photosensitive material in the form of "a photosensitive sheet" to an automatic developing machine. More particularly, the invention further relates to a photosensitive sheet delivering method and apparatus in which a photosensitive sheet is delivered to a sheet introducing device of the automatic developing machine at high speed.
If plural photosensitive sheets are processed by successive delivery to an automatic developing machine, in order to fully utilize the maximum processing ability of the automatic developing machine, it is preferable that the processing interval between the rear edge of the preceding photosensitive sheet and the front edge of the following photosensitive sheet be made as small as possible. In general, the operation of a mechanism for extracting photosensitive sheets one after another from a cassette or a magazine is intermittent. Therefore, it is necessary that a photosensitive sheet be delivered to the sheet introducing device of the automatic developing machine at high speed to reduce the distance between the sheet and the photosensitive sheet which was previously processed.
It is necessary that the timing of suspending the driving of the delivery device which delivers photosensitive sheets to the automatic developing machine be set according to a detecting technique in which the position of a photosensitive sheet delivered is positively and accurately detected. The timing should occur after the top edge of the photosensitive sheet has been positively inserted into the introducing device. Otherwise, the sheet would stop before being caught up by the introducing device. If the timing is too late, then the sheet may suffer from "kinking fog" because the sheet is excessively curved because of the difference between the speeds of the delivering device and the introducing device or it may suffer from scratches which are made by contact and friction.
Two techniques for detecting the insertion of the top edge of the photosensitive sheet into the sheet introducing device of the automatic developing machine are known in the art. One of the two techniques is a direct detection technique. When a photosensitive sheet is inserted between a pair of rollers which form the above-described sheet introducing device, one of the two rollers is caused to rise by as much as the thickness of the photosensitive sheet. With this direct detection technique, this rise is increased by a lever mechanism and is then detected by a limit switch. The other technique is an indirect detection method in which the passage of a photosensitive sheet is detected by a limit switch or a photoelectric detector provided ahead of the sheet introducing device. With this technique it is assumed that when a predetermined period of time passes from the time of detection of the passage of the sheet, the top edge of the sheet has been inserted into the sheet introducing device.
In the direct detection technique, in order to prevent erroneous operation it is necessary to accurately adjust the gap between the two rollers in accordance with the thickness of the photosensitive sheets being processed because the operation of the limit switch depends on the gap. Thus, the direct technique is disadvantageous in that it is rather difficult in handling, low in reliability, and requires an intricate mechanism and accordingly a device for practicing this technique has a relatively high manufacturing cost.
On the other hand, in the indirect detection technique, since the driving of the sheet delivering means is suspended when a period of time set by a delay timer elapses following the time of detection, it is necessary to accurately adjust the delay timer. Accordingly, the indirect detection technique is also disadvantageous in that it is low in reliability because of the fluctuations of the delay timer and a device for practicing the technique also has a high manufacturing cost because of the employment of the delay timer.
Thus, another object of the invention is to provide a method and apparatus for delivering photosensitive sheets to an automatic developing machine in which the position of a photosensitive sheet, which determines the timing of suspending the driving of a sheet delivering means which delivers photosensitive sheets to the sheet introducing device of an automatic developing machine at a speed higher than the conveyance speed in the automatic developing machine, is positively and accurately detected thereby eliminating the above-described difficulties accompanying the conventional techniques.